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https://issues.apache.org/jira/browse/HBASE-6236?page=com.atlassian.jira.plugin.system.issuetabpanels:comment-tabpanel&focusedCommentId=13399628#comment-13399628
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Aditya Kishore commented on HBASE-6236:
---------------------------------------
@Jimmy
Currently there are two different locations where hbck sidelines the backup
data.
First one takes the form '/hbck/hbase-xxxxxx' and is used to sideline regions
{code:title=HBaseFsck.java}
857 private Path getSidelineDir() throws IOException {
858 Path hbaseDir = FSUtils.getRootDir(conf);
859 Path hbckDir = new Path(hbaseDir.getParent(), "hbck");
860 Path backupDir = new Path(hbckDir, hbaseDir.getName() + "-"
861 + startMillis);
862 return backupDir;
863 }
{code}
While the second one takes the form of '/hbase-xxxxx' and is used to sideline
the current .META. and \-ROOT\- folders
{code:title=HBaseFsck.java}
960 Path backupDir = new Path(hbaseDir.getParent(), hbaseDir.getName()
+ "-"
961 + startMillis);
{code}
At lease we need to make them standard.
Secondly, I am not sure how pre-creating "/hbck" will solve this problem in a
federated HDFS in all cases. Suppose the root of a cluster is mounted as
"/hbase" in ViewFS then the pre created "/hbck" folder is going to be on a
different namespace volume and renaming of a file from "/hbase/" to "/hbck/" is
going to fail.
> Offline meta repair fails if the HBase base mount point is on a different
> cluster/volume than its parent in a ViewFS or similar FS
> ----------------------------------------------------------------------------------------------------------------------------------
>
> Key: HBASE-6236
> URL: https://issues.apache.org/jira/browse/HBASE-6236
> Project: HBase
> Issue Type: Bug
> Components: hbck
> Reporter: Aditya Kishore
> Assignee: Aditya Kishore
> Fix For: 0.96.0, 0.94.1
>
> Attachments: 6236_trunk.patch, HBASE-6236_94.patch,
> HBASE-6236_trunk.patch, HBASE-6236_trunk.patch
>
>
> While building the .META. and -ROOT- from FS data alone (HBASE-4377), hbck
> tries to move the existing .META. and -ROOT- directories to a backup folder.
> This backup folder is created at the same level as the base HBase folder
> (e.g. /hbase-xxxxxx if the base HBase folder is '/hbase').
> In a federated HDFS like ViewFS and other similar FS implementations, it is
> not possible to rename files/directories across namespace volumes (ViewFS
> guide section 3.5) and as a result hbck crashes.
> A solution to this problem is to create the backup directory under the folder
> where HBase base folder has been mounted. This ensures that source and
> destination of rename operation are on the same namespace volume.
> Patch for 0.94 and trunk is attached for review. The patch modifies the
> location of the backup directory from '/hbase-xxxxxxx' to
> '/hbase/.hbcktmp-xxxxxxx'
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